One of the characters is taken to a private cemetery and shown the grave of a murderer executed in 1926. At that time in France, murderers were always buried in the cemetery of the prison where they were executed.
After developing photographs in her dark room, the photographer goes straight to making a cup of tea/coffee without cleaning nor eve washing her hands. Developing chemicals would have included Potassium Cyanide - a crass error that no professional photographer would make or, at least, survive.